I'd have to say I'd prefer to see Alien 5.
The Predator culture and actual creatures are fascinating and offer much potential, but in my opinion the Predator films are much weaker than the Alien set.
Predator 3 will probably be another AvP2, which has about 10 minutes of the actual creatures doing awesome stuff and most of the movie being hogged some whiny highschool students.
I didn't come to Aliens and Predators to see Bobby Snotnose whine about not being popular enough in his inconsequential highschool, I came to see Yautja prove their mettle against the Kainde Amedha!
Explosions and wanton ignoring of the human race in favour of their timeless battles!
Please, if anyone making either Predator 3 or Aliens 5 sees this, less humans, more Yautja/Aliens!